Always enable mpeg2ts when enable_hls_demuxer is true.

While we have approval to also enable it when proprietary codecs
is false, there's no benefits to doing so since all of the tests
require H264/AAC support which would require proprietary codecs.

If we later add support for VP9/AV1 in TS we can rework the tests
so that only the proprietary ones are behind the buildflag.

R=tmathmeyer

Fixed: 1373993
Bug: 1266991
Change-Id: Ife873cea0b4852859337c0bb88422b39628523b2
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4400396
Commit-Queue: Dale Curtis <dalecurtis@chromium.org>
Auto-Submit: Dale Curtis <dalecurtis@chromium.org>
Reviewed-by: Ted (Chromium) Meyer <tmathmeyer@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1126828}